Patent GB-385618-A (GB)
Title: An improved method of and apparatus for electrically operating or controlling road traffic signals automatically
IPC: G08G1/085
Filed: 1931-06-26
Abstract: 385,618. Road signals for controlling traffic. SCOTT, W. H. and GLENDENNING, S. E., Gothic Works, Norwich. June 26, 1931, Nos. 18571 and 23999. [Class 118 (ii).] In a road-traffic control system in which an electromagnetic driving device energized by impulsesfrom a transmitter, advances the signalling circuit control means through a ratchet and pawl, the timing of the signals is controlled by varying the effective stroke of the pawl. There may be a number of electromagnetic driving devices corresponding to the number of signals each being pulsed in turn by the transmitter to operate the signalling means during display of the corresponding signal. Transmitter. This may be similar to the delay action relay described. in Specification 370,148, [Group XXXVII], and comprisesmagnets 6, 61 which automatically rock an oscillatable armature 7, contacts 8, 8<1> thereon effecting alternate energization and shortcircuiting of the magnets, the electromagnetic driving device or solenoid 1 being energized in series with coil 6<1>. Alternatively, a clockwork or other suitable transmitter may be used. Electromagnetic driving device ; operation. The plunger 12 of solenoid 1 drives, through link 13, carrier 11, and pawl 3, a ratchet wheel 4, Fig. 3, mounted on a shaft 10 geared to a drum controller 2 which effects the signal changes at contacts 28. Pivoted at 27 to the solenoid frame is an arm 23, carrying a roller 24 bearing upon a cam 14 fixed to shaft 10, and adjustable snail cams 20, 21, 22. The latter function as stops for a tappet 18 projecting through a slot 26 in arm 23 and carried on a pivoted arm 19 oscillated by the plunger 12, thus limiting the downward motion of the latter. Steps 17, 15, 16 on cam 14 are adapted to position the tappet 18 over cams 22, 21, 20 respectively, and the gearing -10<1> is such that a corresponding signal change is made as the roller 24 passes the steps, so that cams 20, 21, 22 are operative, during their corresponding signals. These cams may be replaced by a cone or stepped member adapted to be shifted axially by cam 14 to bring the desired part of the cone or step under tappet 18. A main switch 34, 35, 36 is provided, which in the automatic position causes the apparatus to work as above, in the hand position disconnects the transmitter 5 the drum 2 being then rotated by hand, and in the amber position illuminates the amber lamps only. In another embodiment three solenoids 1, Figs. 6 and 8, corresponding to the red, amber and yellow signals are provided, each driving a ratchet wheel 4 on the shaft 10 through a link 13, lever 29 and pawl 3, the stroke of each plunger 12 being controlled by a stop lever 19, oscillated thereby and carrying a pin 30 which bears on a cam 31 adjustably fixed to the solenoid frame. The drum 2, Fig. 9, geared to shaft 10 has sections D and S. The latter closes the signal circuits which light in the sequence green, amber, red, red and amber, green through contacts 28, section D rendering a solenoid 1 operative and short-circuiting the remaining two at each signal change over contacts 281. Alternatively section D could be arranged to connect up the solenoids 1 in the desired order instead of rendering them operative by removing a short-circuit therefrom. A main switch 34 for automatic or hand operation is provided and means for illuminating the amber lamps only may be included. Modifications. The cams 31, Fig. 6, corresponding to the red and green signals may be interconnected so that an adjustment to increase one signal results in a corresponding decrease in the other. Alternatively, these cams may be replaced by a rocking bar pivoted between the corresponding solenoids, the ends of the bar serving as stops for the tappets of the respective solenoids, the stroke of one plunger being thus increased as the other is decreased. In either embodiment the stroke of the driving pawl may be constant, the variation in the motion transmitted being effected by adjusting the length of engagement of the pawl, for example, by using a shield for the ratchet teeth, adjustable about the ratchet wheel axis. The signal cycle period may be varied by altering the rate of impulse transmission from the transmitter. The drum 2 may be replaced by cams for operating the contacts.